An insert described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2004-237438), for example, is known as a cutting insert used for turning processing. The insert described in Patent Document 1 includes a nose cutting edge, a first flat cutting edge (wiper edge), and a second flat cutting edge. Then, a curvature radius of the first flat cutting edge is greater than a curvature radius of the nose cutting edge, and a curvature radius of the second flat cutting edge is greater than the curvature radius of the first flat cutting edge.
In a tip described in Patent Document 1, the curvature radius of the first flat cutting edge is greater than the curvature radius of the nose cutting edge. Accordingly, while a region of the nose cutting edge can be reduced in width, machined surface accuracy may decrease in processing in which a work material is repeatedly cut by the wiper edge.